Redefining the dose of the entomopathogenic fungus Metarhizium brunneum (Ascomycota, Hypocreales) to increase Fe bioavailability and promote plant growth in calcareous and sandy soils

• Published in: Plant and soil Vol. 418; no. 1/2; pp. 387 - 404
• Main Authors: Raya–Díaz, Silvia, Quesada–Moraga, Enrique, Barrón, Vidal, del Campillo, María Carmen, Sánchez–Rodríguez, Antonio Rafael
• Format: Journal Article
• Language: English
• Published: Cham Springer Science + Business Media 01-09-2017; Springer International Publishing; Springer; Springer Nature B.V
• Subjects: Ascomycota; Assaying; Beauveria bassiana; Bioavailability; Biological control; Biomedical and Life Sciences; Calcareous soils; Chlorosis; Conidia; Crystal structure; Crystallinity; Ecology; Entomopathogenic fungi; Environmental aspects; Fungi; Goethite; Hematite; Iron (Nutrient); Life Sciences; Magnetite; Nutrition; Observations; Oxides; Particle size; Pest control; pH effects; Plant growth; Plant nutrition; Plant Physiology; Plant Sciences; Plants (botany); REGULAR ARTICLE; Sandy soils; Soil Science & Conservation; Soils; Sorghum; Non–calcareous soil; Sandy soil; Iron nutrition; Calcareous soil; Plant growth promoter; Iron chlorosis
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-017-3303-0

Background and aims
Entomopathogenic mitosporic ascomycetes
Beauveria, Metarhizium
and
Isaria
sp. are commonly used for pest control but can also serve other, lesser known functions such as increasing nutrient bioavailability or promote plant growth. The objective of this work was to identify the doses of entomopathogenic fungi (EF) to be applied to soil in order to modify iron (Fe) uptake by plants and promote their growth.
Methods
We used an
in vitro
assay to assess the ability of
Beauveria bassiana, Metarhizium brunneum
and
Isaria farinosa
to mobilize Fe from nine Fe oxides differing in composition, particle size and crystallinity, including ferrihydrite, hematite, goethite and magnetite. We also conducted an
in vivo
assay by applying five different doses (viz., 0, 5 × 10
2
, 5 × 10
4
, 5 × 10
6
and 5 × 10
8
conidia ml
−1
) of a conidial suspension of
M. brunneum
to the surface of a calcareous soil, which induced Fe chlorosis and a non–calcareous soil which did not induce chlorosis to explore the ability of the fungus on improving Fe nutrition and plant growth of sorghum and sunflower plants.
Results
In the
in vitro
assay, all three EF increased Fe availability differently depending on particle size and crystallinity, and
I. farinosa
and
B. bassiana
increased the pH of the culture medium, whereas
M. brunneum
did not produce a great effect. In the
in vivo
assay, the highest dose (5 × 10
8
conidia ml
−1
) of
M. brunneum
alleviated Fe chlorosis symptoms of sorghum plants grown in the calcareous soil, and the two highest doses (5 × 10
6
and 5 × 10
8
conidia ml
−1
) increased plant height and inflorescence production of sunflower grown in both soils.
Conclusions
The observed benefits of EF on plant growth and nutrition provide support for more sustainable and cost–effective use of these biocontrol agents.